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カスタム BaseAdapter を使用してリストを作成しようとしています。nullpointerexception エラーが発生しています。データをアダプターに正しくロードできなかったか、ビューが間違っているようです。

以下は私のコードです:
FragmentActivity

public class NewsItemListActivity extends FragmentActivity implements NewsItemListFragment.Callbacks {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_newsitem_list);        
        if (savedInstanceState != null) {
            mActivePosition = savedInstanceState.getInt(STATE_ACTIVE_POSITION);
        }
        if (findViewById(R.id.newsitem_detail_container) != null) {
            listfragment = ((NewsItemListFragment) getSupportFragmentManager()
                    .findFragmentById(R.id.newsitem_list));
            listfragment.setActivateOnItemClick(true);      
        }
}

Activity_newsitem_list レイアウト

<fragment xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/newsitem_list"
    android:name="com.example.app.NewsItemListFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:layout_marginLeft="16dp"
    android:layout_marginRight="16dp"
    tools:context=".NewsItemListActivity"
    tools:layout="@android:layout/list_content" />


リストフラグメント

public class NewsItemListFragment extends ListFragment implements LoaderManager.LoaderCallbacks<List<NewsData>>{

    List<NewsData> listdata;
    CustomAdapter mListAdapter;

    public NewsItemListFragment() {
    }

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) {
        super.onActivityCreated(savedInstanceState);
        // Initially there is no data 
        setEmptyText("No Data Here");

        mListAdapter = new CustomAdapter(getActivity(),listdata);
        setListAdapter(mListAdapter);

        // Start out with a progress indicator.
        setListShown(false);

        getLoaderManager().initLoader(0, null, this);
    }

    @Override
    public Loader<List<NewsData>> onCreateLoader(int arg0, Bundle arg1) {
        return new ListLoader(getActivity());
    }
    @Override
    public void onLoadFinished(Loader<List<NewsData>> arg0,
            List<NewsData> data) {
            listdata = data;
        mListAdapter.notifyDataSetChanged();
        if (isResumed()) {
            setListShown(true);
        } else {
            setListShownNoAnimation(true);
        }       
    }
    @Override
    public void onLoaderReset(Loader<List<NewsData>> arg0) {
        listdata = null;
    }

}

ベースアダプター

public class CustomAdapter extends BaseAdapter{

    private List<NewsData> list;
    Context context;
    public CustomAdapter(Context c,List<NewsData> data){
        context = c;
        list = data;    
    }
    @Override
    public int getCount() {
        return list.size();
    }

    @Override
    public Object getItem(int position) {
        return list.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        View view;

        if (convertView == null) {
            LayoutInflater mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            view = mInflater.inflate(R.layout.list_layout, parent, false);
        } else {
            view = convertView;
        }

        NewsData item = list.get(position);
        ((TextView)view.findViewById(R.id.subject)).setText(item.getSubject());
        ((TextView)view.findViewById(R.id.cdate)).setText(item.getCDate());

        return view;
    }

}

NewsData クラス

public class NewsData {
    public String id;
    public String subject; 
    public String cdate;

        public NewsData(String id, String subject,String cdate) {
            this.id = id;
            this.subject = subject;
            this.cdate = cdate;
        }
        public String getId() {
            return id;
        }
        public void setId(String id) {
            this.id = id;
        }
        public String getSubject() {
            return subject;
        }
        public void setSubject(String subject) {
            this.subject = subject;
        }
        ........
}

ローダーを追加

@Override
    public List<NewsData> loadInBackground() {
        List<NewsData> entries = null;
            .....
            return entries.add(new NewsData(i,subject,cdate));
}

@Override 
    public void deliverResult(List<NewsData> listOfData) {
        List<NewsData> oldNews = listOfData;
        mNewsData = listOfData;

        if (isStarted()) {
            // If the Loader is currently started, we can immediately
            // deliver its results.
            super.deliverResult(listOfData);
        }
    }

エラーログ

04-05 07:31:17.951: E/AndroidRuntime(1495): FATAL EXCEPTION: main
04-05 07:31:17.951: E/AndroidRuntime(1495): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.appapp/com.example.appapp.NewsItemListActivity}: java.lang.NullPointerException
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2059)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2084)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.ActivityThread.access$600(ActivityThread.java:130)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1195)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.os.Handler.dispatchMessage(Handler.java:99)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.os.Looper.loop(Looper.java:137)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.ActivityThread.main(ActivityThread.java:4745)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at java.lang.reflect.Method.invokeNative(Native Method)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at java.lang.reflect.Method.invoke(Method.java:511)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at dalvik.system.NativeStart.main(Native Method)
04-05 07:31:17.951: E/AndroidRuntime(1495): Caused by: java.lang.NullPointerException
04-05 07:31:17.951: E/AndroidRuntime(1495):     at com.example.appapp.CustomAdapter.getCount(CustomAdapter.java:25)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.widget.ListView.setAdapter(ListView.java:460)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.ListFragment.setListAdapter(ListFragment.java:182)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at com.example.appapp.NewsItemListFragment.onActivityCreated(NewsItemListFragment.java:96)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.Fragment.performActivityCreated(Fragment.java:1468)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:931)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1088)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1070)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.FragmentManagerImpl.dispatchActivityCreated(FragmentManager.java:1861)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:547)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1163)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.Activity.performStart(Activity.java:5018)
04-05 07:31:17.951: E/AndroidRuntime(1495):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2032)
04-05 07:31:17.951: E/AndroidRuntime(1495):     ... 11 more

長文すみません…

4

1 に答える 1

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実際には非常に単純です。

List<NewsData> listdata
初期化していないことがわかります NullPointerException。

それを使用する前に、そのリストの新しいインスタンスを作成する必要があります。

listdata = new List<NewsData> ()あなたに書いてOnCreate ()、その中にいくつかの項目を追加してくださいList

于 2013-04-05T07:59:35.517 に答える